D vs L vs DL/LD Cultures

[Scarlettbri12]

Hello all,

I was wondering if anyone had any more information on categorizing LAB as D/L/DL? I saw it mentioned in a comment by Linuxboy on this forum ( https://cheeseforum.org/forum/index.php/topic,524.0.html ) and found it very interesting.

I was able to find a few sources that mentioned something similar; namely a website ( http://dairytechnologist.com/starter-culture-basics/ ) that leaves a lot to be questioned, a cheese culture catalog from Chr Hansen ( https://hjemmeriet.com/da/ChrHansen/Brochures/GlobalCheeseCultureCatalogue_EN-2014.pdf pg. 11) that mentions something similar to the website, and the knowledge that these bacteria tend to form either L or D -lactate isomers (or both). How can I find more information on this, and how can I put it to good use in choosing cultures for different cheeses? It's hard to really figure much out; like if it is for the main LAB, or adjuncts. If possible I'd like to wrap my head around understanding it

Thank you!

[mikekchar]

I'll preface by saying that I do not know very much at all.  In fact very probably less than you do, but I'll write what I know for the benefit of people who know less than me :-)

Lactic acid bacteria (LAB) are the starter cultures that we use for converting sugars in the milk into acid.  When we talk about "starter cultures" we are normally talking about these lactic acid bacteria.  There are lots of different LAB, but I think the 3 main kinds are lactobacilus, lactococcus and streptococcus.  I'm sure there are many exceptions, but bacteria from the lactobacilis and streptococcus "genus" tend to be thermophilic and bacteria from the lactococcus "genus" seems to be mesophilic.  The main things about these lactic acid bacteria is that they eat sugar and produce lactic acid as a result.  This makes the milk sour and is necessary in cheese making.  It seems that there are some bacteria that only produce lactic acid and very little in terms of other by products.

You can kind of think of the "genus" (general) name as being the surname for your family.  Just like your surname can't identify *you*, the genus alone can't identify a single kind of bacteria.  Additionally you need a "species" (specific) name.  For example streptococcus thermophilic is a full name for a kind of bacteria.  On top of that, there may be a "strain" of bacteria -- a bacteria that is the same kind, but just a little bit different.  For example, lactococcus lactus "subspecies" cremoris.  "cremoris" is the subspecies (very specific) name of a particular kind of lactococcus lactus bacteria.  Each of these strains can produce different kinds of flavours, etc.  There is actually a ridiculous variety of these different bacteria (hundreds upon hundreds of commercially used ones).  They all work a little differently and may do different things in combination.

One of the things bacteria (and yeast too!) can produce is diacetyl.  Diacetyl is a compound that produces "buttery" or "caramel" flavours.  The mesophilic cultures that people use tend to generate a fair amount of diacetyl and that's what gives you the really butter flavour in a camembert, for instance.  It seems that when they are talking about "D" cultures, they are talking about cultures that produce diacetyl (yummy buttery flavours).

"L" cultures are from the "leuconostoc" cultures.  As far as I can tell, these cultures are not LAB (they don't produce lactic acid).  However, they work well with lactic acid bacteria.  They produce "dextrines" which are sticky, slimy carbohydrates from starch or other sugars.  This gives you a nice mouth feel (think full, gelatine like, creamy mouth feels).  Apparently these are important in the production of sauerkraut (unrelated factoid).

"DL" cultures are apparently cultures that are "leuconostoc" cultures (produce nice creamy, sticky mouth feel) that also generate diacetyl (buttery flavours).  You can see why they might be popular for some cheeses.

The word "adjunct" usually means something you add to a product that is not completely necessary, or is used as a replacement for something else.  As I'm originally an avid beer brewer, "adjunct" to me means adding something like corn to a beer instead of adding barley malt.  You don't need it, but you add it to achieve specific flavour results (or to reduce cost).  So I think "adjunct" is being used in a similar fashion here.  It is adding extra bacteria that isn't necessary to make cheese, but is added to achieve specific effects.    Bacteria that produces gas to make eyes in the cheese, or that processes diacetyl for buttery flavour, or that generates dextrines for mouthfeel, etc.

I hope that at least helps people with some of the vocabulary.

[Scarlettbri12]

@mikekchar This is all very good information! I did know quite a bit of it, but it is always good to know I'm on the right track 

I was hoping that someone could back up or explain linuxboy's comment on DL cultures being good for gouda style cheeses and find out a general guide, using L vs D vs DL classifications, which cultures are best for which types of cheese! I think it would be immensely helpful, as I could then add some more criteria to choosing correct cultures per style of cheese and understanding the nuanced behavior and profiles that come from each. 

I'm currently going through spec sheets for each culture mixture/species of starter/adjuncts and attempting to classify using the knowledge found (and mentioned by mikekchar) and the producer descriptions to fully figure out which cultures are best to choose. There is no real great guide I've found, so it's not been easy. I've recently found the book Cheese & Microbes, and plan on diving into that as well!

I've scoured this website as well as linuxboy's website (using the wayback machine) and found all of his information given to be extremely useful. I just wish he was still around to explain. I love learning more and more